A computer network is a collection of interconnected computing devices that exchange data and share resources. In a packet-based network, such as the Internet, the computing devices communicate data by dividing the data into small blocks called packets. The packets are individually routed across the network from a source device to a destination device. The destination device extracts the data from the packets and assembles the data into its original form. Dividing the data into packets enables the source device to resend only those individual packets that may be lost during transmission.
Certain devices within a network, referred to as routers, maintain routing information that describes available routes through the network. Each route defines a path between two locations on the network. Upon receiving an incoming data packet, the router examines header information within the packet to identify the destination for the packet. Based on the header information, the router accesses the routing information, selects an appropriate route for the packet and forwards the packet accordingly.
Recently, development of certain applications, such as Voice-over-Internet Protocol (VoIP) applications have led to the development of network devices that act as gateways capable of interconnecting public system telephone networks (PSTNs), or more generally circuit-switched networks, to packet-switched networks, such as the Internet. These “media gateways” enable subscribers of the PSTN to initiate and receive calls from subscribers of the VoIP applications by transcoding the PSTN voice signals and VoIP packets into packets and voice signals, respectively. By joining these two networks, the media gateways enable interoperability between two diverse technologies, while increasing the calling options of the networks' respective subscribers.
In order to interconnect these two network types, routers at the edge of the packet-switched networks, i.e., edge routers, interact with the media gateways at the edge of the circuit-switched networks. A media gateway may, for example, arrange for dedicated routes through a packet-switched network to handle calls originating from a PSTN subscriber. The media gateway arranges these dedicated routes by transmitting messages via a protocol to an edge router, and in response, the edge router establishes the dedicated routes through the packet-switched network.
Commonly, the media gateway may also establish secondary, or standby, routes through the packet-switched networks that remain unused or only partially used, which enables them to accept voice traffic should communications fail over the original route. Often times, the standby routes require the media gateway to elect a backup router, which it may specify via the virtual router redundancy protocol (VRRP). In the event communications fail over the original dedicated routes, the media gateway may detect such failure, elect the backup router as the active router via the VRRP, and begin forwarding voice traffic over the standby routes.
While enabling the election of the backup router, VRRP is limited and inflexible. For example, VRRP limits media gateways with respect to the richness of the redundancy supported between the hosts and the media gateways. Media gateways employing VRRP may be slow to fail over to stand by routes, i.e., begin forwarding voice traffic over the standby routes, after detecting a communication failure. Moreover, once the previous route recovers from the failure VRRP typically reverts back to forwarding voice traffic via the previous route. Slow failover and excessive reverting by the media gateway may cause communication delays that affect the quality of the voice traffic.